When
"The Office" approached
Josh Groban about guest-starring in an episode, it was not a situation where the producers had to send a bunch of DVDs so he could get up to speed on the show. Groban is a certified "Office" fanboy.

"I had loved the DVDs of the British version, and when it came to America, we watched and thought, What a brilliant job they did ... making it its own hilarious entity," the Grammy-nominated singer and sometime actor said Thursday (Oct. 13). "I've been watching every season, and when I got the call to be on it I was really, really thrilled."

Groban guests in Thursday's episode, "Garden Party," as Andy's (
Ed Helms) younger brother. The show also features
Stephen Collins and
Dee Wallace as Andy's parents, who attend a garden party he throws at Schrute Farm to celebrate his promotion to branch manager. We'll also get to see some of the sibling rivalry Andy feels toward his little brother.

"For whatever reason being the second-born, somehow I kind of stole his name from him," Groban says. "He was originally Walter Jr., but then they named me Walter Jr. He kind of wound up being a little bit more happy-go-lucky, he's very successful -- he almost fell up in a way. Of course he likes singing, he's been very successful in business, he kind of can do no wrong in the eyes of his parents."

All of which, of course, gets under Andy's skin in a major way. But where Andy feels competition, Walter Jr. is just happy to see his bro.

"I think Walter Jr. loves Andy to death," Groban says. "For the most part, I'd tend to guess that he's a bit ignorant to the fact that Andy is competitive [with him] or is feeling left out. Walter Jr. thinks the world of his older brother. He looks up to him, even though he's been more successful, and always can't wait to see him. That said, subconsciously there's always a bit of a rivalry going on in a family, whether you choose to admit or not, and most of it is sparked by the dad, who favors Walter Jr. more than Andy."

And yes, there will be singing. How could there not be, given Andy's character and Groban's day job?

"The episode shows a tremendous musical rivalry in the family, not only between Andy and Walter Jr., but also [Walter Sr.] is quite musical and has quite a voice," Groban says. "The whole musical tapestry of the Bernard family comes to light."

"The Office" airs at 9 p.m. ET Thursday (Oct. 13) on NBC. Take a look at a couple of Groban's scenes: